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<FONT color="green">001</FONT>    package project3.three;<a name="line.1"></a>
<FONT color="green">002</FONT>    <a name="line.2"></a>
<FONT color="green">003</FONT>    import java.util.HashMap;<a name="line.3"></a>
<FONT color="green">004</FONT>    <a name="line.4"></a>
<FONT color="green">005</FONT>    import project3.lex.Constant;<a name="line.5"></a>
<FONT color="green">006</FONT>    import project3.lex.Identifier;<a name="line.6"></a>
<FONT color="green">007</FONT>    import project3.lex.Lex;<a name="line.7"></a>
<FONT color="green">008</FONT>    import project3.lex.TokenType;<a name="line.8"></a>
<FONT color="green">009</FONT>    import project3.PredicateList;<a name="line.9"></a>
<FONT color="green">010</FONT>    <a name="line.10"></a>
<FONT color="green">011</FONT>    /**<a name="line.11"></a>
<FONT color="green">012</FONT>     * A Rule in the datalog program.<a name="line.12"></a>
<FONT color="green">013</FONT>     *<a name="line.13"></a>
<FONT color="green">014</FONT>     * &lt;p&gt;<a name="line.14"></a>
<FONT color="green">015</FONT>     * Syntax: &lt;b&gt;Rule&lt;/b&gt; -&amp;rarr; &lt;b&gt;Head&lt;/b&gt; ":-" &lt;b&gt;PredicateList&lt;/b&gt; "."<a name="line.15"></a>
<FONT color="green">016</FONT>     * <a name="line.16"></a>
<FONT color="green">017</FONT>     * &lt;p&gt;<a name="line.17"></a>
<FONT color="green">018</FONT>     * &lt;pre&gt;<a name="line.18"></a>
<FONT color="green">019</FONT>     * Domain Definition:<a name="line.19"></a>
<FONT color="green">020</FONT>     *     head : Head<a name="line.20"></a>
<FONT color="green">021</FONT>     *     tail : PredicateList<a name="line.21"></a>
<FONT color="green">022</FONT>     *<a name="line.22"></a>
<FONT color="green">023</FONT>     * Instance Invariant:<a name="line.23"></a>
<FONT color="green">024</FONT>     *     head &amp;ne; null AND<a name="line.24"></a>
<FONT color="green">025</FONT>     *     tail &amp;ne; null<a name="line.25"></a>
<FONT color="green">026</FONT>     * &lt;/pre&gt;<a name="line.26"></a>
<FONT color="green">027</FONT>     *<a name="line.27"></a>
<FONT color="green">028</FONT>     * Last Modified: 21 Feb 2006<a name="line.28"></a>
<FONT color="green">029</FONT>     *<a name="line.29"></a>
<FONT color="green">030</FONT>     * @author Scott N. Woodfield<a name="line.30"></a>
<FONT color="green">031</FONT>     * @version 1.0<a name="line.31"></a>
<FONT color="green">032</FONT>     * @see<a name="line.32"></a>
<FONT color="green">033</FONT>     *   &lt;a href=<a name="line.33"></a>
<FONT color="green">034</FONT>     *      "../../srchtml/project3/Rule.html"<a name="line.34"></a>
<FONT color="green">035</FONT>     *      &gt;Source Code<a name="line.35"></a>
<FONT color="green">036</FONT>     *   &lt;/a&gt;<a name="line.36"></a>
<FONT color="green">037</FONT>     */<a name="line.37"></a>
<FONT color="green">038</FONT>    public class Rule<a name="line.38"></a>
<FONT color="green">039</FONT>        extends Node<a name="line.39"></a>
<FONT color="green">040</FONT>    {<a name="line.40"></a>
<FONT color="green">041</FONT>    //Domain Implementation<a name="line.41"></a>
<FONT color="green">042</FONT>        /**<a name="line.42"></a>
<FONT color="green">043</FONT>         * The head of the &lt;b&gt;Rule&lt;/b&gt;.<a name="line.43"></a>
<FONT color="green">044</FONT>         * @see<a name="line.44"></a>
<FONT color="green">045</FONT>         *   &lt;a href=<a name="line.45"></a>
<FONT color="green">046</FONT>         *      "../../srchtml/project3/Rule.html#head"<a name="line.46"></a>
<FONT color="green">047</FONT>         *      &gt;Source Code<a name="line.47"></a>
<FONT color="green">048</FONT>         *   &lt;/a&gt;<a name="line.48"></a>
<FONT color="green">049</FONT>         */<a name="line.49"></a>
<FONT color="green">050</FONT>        protected Head head;<a name="line.50"></a>
<FONT color="green">051</FONT>    <a name="line.51"></a>
<FONT color="green">052</FONT>        /**<a name="line.52"></a>
<FONT color="green">053</FONT>         * The tail of the &lt;b&gt;Rule&lt;/b&gt;.<a name="line.53"></a>
<FONT color="green">054</FONT>         * @see<a name="line.54"></a>
<FONT color="green">055</FONT>         *   &lt;a href=<a name="line.55"></a>
<FONT color="green">056</FONT>         *      "../../srchtml/project3/Rule.html#tail"<a name="line.56"></a>
<FONT color="green">057</FONT>         *      &gt;Source Code<a name="line.57"></a>
<FONT color="green">058</FONT>         *   &lt;/a&gt;<a name="line.58"></a>
<FONT color="green">059</FONT>         */<a name="line.59"></a>
<FONT color="green">060</FONT>        protected PredicateList tail;<a name="line.60"></a>
<FONT color="green">061</FONT>        <a name="line.61"></a>
<FONT color="green">062</FONT>    //Constructors<a name="line.62"></a>
<FONT color="green">063</FONT>        /**<a name="line.63"></a>
<FONT color="green">064</FONT>         * Constructs a &lt;b&gt;Rule&lt;/b&gt; from the tokens in the lexical analyzer.<a name="line.64"></a>
<FONT color="green">065</FONT>         *               <a name="line.65"></a>
<FONT color="green">066</FONT>         * &lt;p&gt;<a name="line.66"></a>
<FONT color="green">067</FONT>         * &lt;table&gt;<a name="line.67"></a>
<FONT color="green">068</FONT>         *   &lt;tr&gt;<a name="line.68"></a>
<FONT color="green">069</FONT>         *     &lt;td valign=top&gt;<a name="line.69"></a>
<FONT color="green">070</FONT>         *       &lt;b&gt;Precondition&lt;/b&gt;:<a name="line.70"></a>
<FONT color="green">071</FONT>         *     &lt;/td&gt;<a name="line.71"></a>
<FONT color="green">072</FONT>         *     &lt;td valign=top&gt;<a name="line.72"></a>
<FONT color="green">073</FONT>         *       lex &amp;ne; null<a name="line.73"></a>
<FONT color="green">074</FONT>         *     &lt;/td&gt;<a name="line.74"></a>
<FONT color="green">075</FONT>         *     &lt;td valign=top&gt;<a name="line.75"></a>
<FONT color="green">076</FONT>         *       AND<a name="line.76"></a>
<FONT color="green">077</FONT>         *     &lt;/td&gt;<a name="line.77"></a>
<FONT color="green">078</FONT>         *   &lt;/tr&gt;<a name="line.78"></a>
<FONT color="green">079</FONT>         *   &lt;tr&gt;<a name="line.79"></a>
<FONT color="green">080</FONT>         *     &lt;td valign=top&gt;<a name="line.80"></a>
<FONT color="green">081</FONT>         *       &amp;nbsp;<a name="line.81"></a>
<FONT color="green">082</FONT>         *     &lt;/td&gt;<a name="line.82"></a>
<FONT color="green">083</FONT>         *     &lt;td valign=top&gt;<a name="line.83"></a>
<FONT color="green">084</FONT>         *       &amp;exist;&lt;sub&gt;i&lt;/sub&gt;<a name="line.84"></a>
<FONT color="green">085</FONT>         *          (&amp;exist;&lt;sub&gt;j&lt;/sub&gt; (ValidHead(lex[0..i]) AND<a name="line.85"></a>
<FONT color="green">086</FONT>         *                  lex[i+1].getTokenType() == TokenType.COLON_DASH AND<a name="line.86"></a>
<FONT color="green">087</FONT>         *                  ValidPredicateList(lex[i+2..j]) AND<a name="line.87"></a>
<FONT color="green">088</FONT>         *                  lex[j+1].getTokenType() == TokenType.PERIOD))<a name="line.88"></a>
<FONT color="green">089</FONT>         *     &lt;/td&gt;<a name="line.89"></a>
<FONT color="green">090</FONT>         *     &lt;td&gt;<a name="line.90"></a>
<FONT color="green">091</FONT>         *     &lt;/td&gt;<a name="line.91"></a>
<FONT color="green">092</FONT>         *   &lt;/tr&gt;<a name="line.92"></a>
<FONT color="green">093</FONT>         *   &lt;tr&gt;<a name="line.93"></a>
<FONT color="green">094</FONT>         *     &lt;td valign=top&gt;<a name="line.94"></a>
<FONT color="green">095</FONT>         *       &lt;b&gt;Postcondition&lt;/b&gt;:<a name="line.95"></a>
<FONT color="green">096</FONT>         *     &lt;/td&gt;<a name="line.96"></a>
<FONT color="green">097</FONT>         *     &lt;td valign=top&gt;<a name="line.97"></a>
<FONT color="green">098</FONT>         *       &amp;exist;&lt;sub&gt;i&lt;/sub&gt;<a name="line.98"></a>
<FONT color="green">099</FONT>         *          (&amp;exist;&lt;sub&gt;j&lt;/sub&gt; (head = new Head(lex[0..i]) AND<a name="line.99"></a>
<FONT color="green">100</FONT>         *              tail = new PredicateList(lex[i+2..j]) AND<a name="line.100"></a>
<FONT color="green">101</FONT>         *                  lex[j+1].getTokenType() == TokenType.PERIOD))<a name="line.101"></a>
<FONT color="green">102</FONT>         *     &lt;/td&gt;<a name="line.102"></a>
<FONT color="green">103</FONT>         *     &lt;td valign=top&gt;<a name="line.103"></a>
<FONT color="green">104</FONT>         *     &lt;/td&gt;<a name="line.104"></a>
<FONT color="green">105</FONT>         *   &lt;/tr&gt;<a name="line.105"></a>
<FONT color="green">106</FONT>         * &lt;/table&gt;<a name="line.106"></a>
<FONT color="green">107</FONT>         *<a name="line.107"></a>
<FONT color="green">108</FONT>         * @throws ParserException<a name="line.108"></a>
<FONT color="green">109</FONT>         *<a name="line.109"></a>
<FONT color="green">110</FONT>         * @param lex the lexical analyzer we will create a &lt;b&gt;Rule&lt;/b&gt; from.<a name="line.110"></a>
<FONT color="green">111</FONT>         * @see<a name="line.111"></a>
<FONT color="green">112</FONT>         *   &lt;a href=<a name="line.112"></a>
<FONT color="green">113</FONT>         *      "../../srchtml/project3/Rule.html#LexConstructor"<a name="line.113"></a>
<FONT color="green">114</FONT>         *      &gt;Source Code<a name="line.114"></a>
<FONT color="green">115</FONT>         *   &lt;/a&gt;<a name="line.115"></a>
<FONT color="green">116</FONT>         */<a name="line.116"></a>
<FONT color="green">117</FONT>        public Rule(Lex lex)<a name="line.117"></a>
<FONT color="green">118</FONT>            throws ParserException<a name="line.118"></a>
<FONT color="green">119</FONT>        {<a name="line.119"></a>
<FONT color="green">120</FONT>            head = new Head(lex);<a name="line.120"></a>
<FONT color="green">121</FONT>            checkFor(lex, TokenType.COLON_DASH);<a name="line.121"></a>
<FONT color="green">122</FONT>            tail = new PredicateList(lex);<a name="line.122"></a>
<FONT color="green">123</FONT>            checkFor(lex, TokenType.PERIOD);<a name="line.123"></a>
<FONT color="green">124</FONT>        }<a name="line.124"></a>
<FONT color="green">125</FONT>    <a name="line.125"></a>
<FONT color="green">126</FONT>    //Queries<a name="line.126"></a>
<FONT color="green">127</FONT>        /**<a name="line.127"></a>
<FONT color="green">128</FONT>         * Converts the Rule to a lexical representation.<a name="line.128"></a>
<FONT color="green">129</FONT>         *<a name="line.129"></a>
<FONT color="green">130</FONT>         * &lt;/pre&gt;<a name="line.130"></a>
<FONT color="green">131</FONT>         * &lt;p&gt;<a name="line.131"></a>
<FONT color="green">132</FONT>         * &lt;table&gt;<a name="line.132"></a>
<FONT color="green">133</FONT>         *   &lt;tr&gt;<a name="line.133"></a>
<FONT color="green">134</FONT>         *     &lt;td valign=top&gt;<a name="line.134"></a>
<FONT color="green">135</FONT>         *       &lt;b&gt;Precondition&lt;/b&gt;:<a name="line.135"></a>
<FONT color="green">136</FONT>         *     &lt;/td&gt;<a name="line.136"></a>
<FONT color="green">137</FONT>         *     &lt;td valign=top&gt;<a name="line.137"></a>
<FONT color="green">138</FONT>         *       none<a name="line.138"></a>
<FONT color="green">139</FONT>         *     &lt;/td&gt;<a name="line.139"></a>
<FONT color="green">140</FONT>         *     &lt;td valign=top&gt;<a name="line.140"></a>
<FONT color="green">141</FONT>         *     &lt;/td&gt;<a name="line.141"></a>
<FONT color="green">142</FONT>         *   &lt;/tr&gt;<a name="line.142"></a>
<FONT color="green">143</FONT>         *   &lt;tr&gt;<a name="line.143"></a>
<FONT color="green">144</FONT>         *     &lt;td valign=top&gt;<a name="line.144"></a>
<FONT color="green">145</FONT>         *       &lt;b&gt;Postcondition&lt;/b&gt;:<a name="line.145"></a>
<FONT color="green">146</FONT>         *     &lt;/td&gt;<a name="line.146"></a>
<FONT color="green">147</FONT>         *     &lt;td valign=top&gt;<a name="line.147"></a>
<FONT color="green">148</FONT>         *       result = head.toString() + ":-" + tail.toString() + "."<a name="line.148"></a>
<FONT color="green">149</FONT>         *     &lt;/td&gt;<a name="line.149"></a>
<FONT color="green">150</FONT>         *     &lt;td valign=top&gt;<a name="line.150"></a>
<FONT color="green">151</FONT>         *     &lt;/td&gt;<a name="line.151"></a>
<FONT color="green">152</FONT>         *   &lt;/tr&gt;<a name="line.152"></a>
<FONT color="green">153</FONT>         * &lt;/table&gt;<a name="line.153"></a>
<FONT color="green">154</FONT>         *<a name="line.154"></a>
<FONT color="green">155</FONT>         * @return the string representation of a &lt;b&gt;Rule&lt;/b&gt;<a name="line.155"></a>
<FONT color="green">156</FONT>         * @see<a name="line.156"></a>
<FONT color="green">157</FONT>         *   &lt;a href=<a name="line.157"></a>
<FONT color="green">158</FONT>         *      "../../srchtml/project3/Rule.html#toString"<a name="line.158"></a>
<FONT color="green">159</FONT>         *      &gt;Source Code<a name="line.159"></a>
<FONT color="green">160</FONT>         *   &lt;/a&gt;<a name="line.160"></a>
<FONT color="green">161</FONT>         */<a name="line.161"></a>
<FONT color="green">162</FONT>        public String toString()<a name="line.162"></a>
<FONT color="green">163</FONT>        {<a name="line.163"></a>
<FONT color="green">164</FONT>            StringBuffer result = new StringBuffer();<a name="line.164"></a>
<FONT color="green">165</FONT>            result.append(head.toString());<a name="line.165"></a>
<FONT color="green">166</FONT>            result.append(":-");<a name="line.166"></a>
<FONT color="green">167</FONT>            result.append(tail.toString());<a name="line.167"></a>
<FONT color="green">168</FONT>            result.append(".");<a name="line.168"></a>
<FONT color="green">169</FONT>            return result.toString();<a name="line.169"></a>
<FONT color="green">170</FONT>        }<a name="line.170"></a>
<FONT color="green">171</FONT>    <a name="line.171"></a>
<FONT color="green">172</FONT>        /**<a name="line.172"></a>
<FONT color="green">173</FONT>         * Determines wheter this rule can show that the predicate is true.<a name="line.173"></a>
<FONT color="green">174</FONT>         *<a name="line.174"></a>
<FONT color="green">175</FONT>         * &lt;p&gt;<a name="line.175"></a>
<FONT color="green">176</FONT>         * &lt;table&gt;<a name="line.176"></a>
<FONT color="green">177</FONT>         *   &lt;tr&gt;<a name="line.177"></a>
<FONT color="green">178</FONT>         *     &lt;td valign=top&gt;<a name="line.178"></a>
<FONT color="green">179</FONT>         *       &lt;b&gt;Precondition&lt;/b&gt;:<a name="line.179"></a>
<FONT color="green">180</FONT>         *     &lt;/td&gt;<a name="line.180"></a>
<FONT color="green">181</FONT>         *     &lt;td valign=top&gt;<a name="line.181"></a>
<FONT color="green">182</FONT>         *       predicate &amp;ne; null<a name="line.182"></a>
<FONT color="green">183</FONT>         *     &lt;/td&gt;<a name="line.183"></a>
<FONT color="green">184</FONT>         *     &lt;td valign=top&gt;<a name="line.184"></a>
<FONT color="green">185</FONT>         *     &lt;/td&gt;<a name="line.185"></a>
<FONT color="green">186</FONT>         *   &lt;/tr&gt;<a name="line.186"></a>
<FONT color="green">187</FONT>         *   &lt;tr&gt;<a name="line.187"></a>
<FONT color="green">188</FONT>         *     &lt;td valign=top&gt;<a name="line.188"></a>
<FONT color="green">189</FONT>         *       &lt;b&gt;Postcondition&lt;/b&gt;:<a name="line.189"></a>
<FONT color="green">190</FONT>         *     &lt;/td&gt;<a name="line.190"></a>
<FONT color="green">191</FONT>         *     &lt;td valign=top&gt;<a name="line.191"></a>
<FONT color="green">192</FONT>         *       result = for every variable in the tail that exists in<a name="line.192"></a>
<FONT color="green">193</FONT>         *                head we substitutie the corresponding constant<a name="line.193"></a>
<FONT color="green">194</FONT>         *                in the predicate and we can find a set of<a name="line.194"></a>
<FONT color="green">195</FONT>         *                constants from the domain that make the tail<a name="line.195"></a>
<FONT color="green">196</FONT>         *                true, then return true, else return false.<a name="line.196"></a>
<FONT color="green">197</FONT>         *     &lt;/td&gt;<a name="line.197"></a>
<FONT color="green">198</FONT>         *     &lt;td valign=top&gt;<a name="line.198"></a>
<FONT color="green">199</FONT>         *     &lt;/td&gt;<a name="line.199"></a>
<FONT color="green">200</FONT>         *   &lt;/tr&gt;<a name="line.200"></a>
<FONT color="green">201</FONT>         * &lt;/table&gt;<a name="line.201"></a>
<FONT color="green">202</FONT>         *<a name="line.202"></a>
<FONT color="green">203</FONT>         * @throws ParserException<a name="line.203"></a>
<FONT color="green">204</FONT>         *<a name="line.204"></a>
<FONT color="green">205</FONT>         * @param predicate the predicate (with all constants) we are going to<a name="line.205"></a>
<FONT color="green">206</FONT>         *                    test.<a name="line.206"></a>
<FONT color="green">207</FONT>         * <a name="line.207"></a>
<FONT color="green">208</FONT>         * @return true iff after substituting all of the constants of the predicate<a name="line.208"></a>
<FONT color="green">209</FONT>         *              into the corresponding variables of the head of the rule,<a name="line.209"></a>
<FONT color="green">210</FONT>         *              can we find a substitution for the remaining free variables<a name="line.210"></a>
<FONT color="green">211</FONT>         *              that make it true.<a name="line.211"></a>
<FONT color="green">212</FONT>         * @see<a name="line.212"></a>
<FONT color="green">213</FONT>         *   &lt;a href=<a name="line.213"></a>
<FONT color="green">214</FONT>         *      "../../srchtml/project3/Rule.html#prove"<a name="line.214"></a>
<FONT color="green">215</FONT>         *      &gt;Source Code<a name="line.215"></a>
<FONT color="green">216</FONT>         *   &lt;/a&gt;<a name="line.216"></a>
<FONT color="green">217</FONT>         */<a name="line.217"></a>
<FONT color="green">218</FONT>        public boolean prove(Predicate predicate)<a name="line.218"></a>
<FONT color="green">219</FONT>            throws ParserException<a name="line.219"></a>
<FONT color="green">220</FONT>        {<a name="line.220"></a>
<FONT color="green">221</FONT>             assert predicate != null;<a name="line.221"></a>
<FONT color="green">222</FONT>    <a name="line.222"></a>
<FONT color="green">223</FONT>             boolean result = false;<a name="line.223"></a>
<FONT color="green">224</FONT>             if(head.matches(predicate)){<a name="line.224"></a>
<FONT color="green">225</FONT>                 PredicateList predicateList = new PredicateList(tail);<a name="line.225"></a>
<FONT color="green">226</FONT>                 predicateList.setVariables(head.unify(predicate));<a name="line.226"></a>
<FONT color="green">227</FONT>                 result = predicateList.evaluate();<a name="line.227"></a>
<FONT color="green">228</FONT>             };<a name="line.228"></a>
<FONT color="green">229</FONT>             return result;<a name="line.229"></a>
<FONT color="green">230</FONT>        }<a name="line.230"></a>
<FONT color="green">231</FONT>    <a name="line.231"></a>
<FONT color="green">232</FONT>    //Commands<a name="line.232"></a>
<FONT color="green">233</FONT>    }<a name="line.233"></a>




























































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